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DRAFT 12/12/64
CONFIDENTIAL
ESTIMATE OF WINTER FLOW OF COLORADO RIVER TO MEXICO
EXCLUDING WELLTON-MOHAWK DRAINAGE WATERS
1.The need is for the best estimate of probable flows to Mexico (excluding Wellton-Mohawk waters) during the next five years, during winter periods when that country's Treaty requests are at 900 cfs., which periods are expected to extend over at least 3 months and probably most of the 5-month winter period each year.
:note: Bur. Recl. Dec. 23 Reply :/note:
2. The Bureau's recent preliminary estimate of minimum winter flows below Imperial Dam (excluding Wellton-Mohawk drainage) is understood to be:
635 cfs. for one month 30 days
735 cfs. for four months 120 days
715 cfs. average for five months 150 days
This estimate is understood to be the basis for the Bureau's advice that the proposed bypass solution to the salinity problem might require releases from storage of 20,000 to 50,000 acre-feet.
3. The Records beginning in 1962 when measures began to reduce flows to Mexico, would best serve as a basis for estimating future flows. The records for the winters of 1962-63, 1963-64, and October and November 1964 of minimum winter inflows below Imperial Dam, excluding releases at that dam, but including gate leakage and returns from the desilting basins, are summarized as follows:
a) Lowest single day (November 7, 1964) 770 cfs.
b) Lowest 15 days (November 1-15, 1964) 830 cfs.
c) Lowest 30 days (consecutive) (January 1963) 900 cfs.
d) Lowest three consecutive months (1962-63) 950 cfs.
e) Lowest five consecutive months (1962-63) 970 cfs.
:note: Langley- past record not good basis :/note:
There appears no basis in the record, including the recent months of October and November 1964 to support an estimate of 715 efs. as an average for the winter months.
4. On the basis of the record, the probable lowest 30-day minimum under present conditions: The two lowest 15-day periods of record are October 1-15 and November 1-15, 1964. The average for these two periods--for a total of 30 days, is--- 850 cfs.
This average of 850 cfs. is considered to be the "minimum base flow under present conditions." It includes no water from above Imperial Dam, except the recorded gate leakage and returns from two desilting basins. It includes no allowance for unavoidable operational wastes, which averaged 150 cfs. in October and November 1964. It does not take into account expected changes in flows in the next five years.
5. Expected Changes in the next five years: The Bureau proposes further reduction in gate leakage at Imperial Dam. Additional drainage wells are scheduled to be in operation in the South Gila Valley in 1965 and in the Yuma Valley probably in 1966. Senator Wash Dam is to be in operation about July 1966. The river is scheduled to be channelized from Imperial Dam to Morelos Dam beginning in 1966.
CONFIDENTIAL

DRAFT 12/12/64
CONFIDENTIAL
ESTIMATE OF WINTER FLOW OF COLORADO RIVER TO MEXICO
EXCLUDING WELLTON-MOHAWK DRAINAGE WATERS
1.The need is for the best estimate of probable flows to Mexico (excluding Wellton-Mohawk waters) during the next five years, during winter periods when that country's Treaty requests are at 900 cfs., which periods are expected to extend over at least 3 months and probably most of the 5-month winter period each year.
:note: Bur. Recl. Dec. 23 Reply :/note:
2. The Bureau's recent preliminary estimate of minimum winter flows below Imperial Dam (excluding Wellton-Mohawk drainage) is understood to be:
635 cfs. for one month 30 days
735 cfs. for four months 120 days
715 cfs. average for five months 150 days
This estimate is understood to be the basis for the Bureau's advice that the proposed bypass solution to the salinity problem might require releases from storage of 20,000 to 50,000 acre-feet.
3. The Records beginning in 1962 when measures began to reduce flows to Mexico, would best serve as a basis for estimating future flows. The records for the winters of 1962-63, 1963-64, and October and November 1964 of minimum winter inflows below Imperial Dam, excluding releases at that dam, but including gate leakage and returns from the desilting basins, are summarized as follows:
a) Lowest single day (November 7, 1964) 770 cfs.
b) Lowest 15 days (November 1-15, 1964) 830 cfs.
c) Lowest 30 days (consecutive) (January 1963) 900 cfs.
d) Lowest three consecutive months (1962-63) 950 cfs.
e) Lowest five consecutive months (1962-63) 970 cfs.
:note: Langley- past record not good basis :/note:
There appears no basis in the record, including the recent months of October and November 1964 to support an estimate of 715 efs. as an average for the winter months.
4. On the basis of the record, the probable lowest 30-day minimum under present conditions: The two lowest 15-day periods of record are October 1-15 and November 1-15, 1964. The average for these two periods--for a total of 30 days, is--- 850 cfs.
This average of 850 cfs. is considered to be the "minimum base flow under present conditions." It includes no water from above Imperial Dam, except the recorded gate leakage and returns from two desilting basins. It includes no allowance for unavoidable operational wastes, which averaged 150 cfs. in October and November 1964. It does not take into account expected changes in flows in the next five years.
5. Expected Changes in the next five years: The Bureau proposes further reduction in gate leakage at Imperial Dam. Additional drainage wells are scheduled to be in operation in the South Gila Valley in 1965 and in the Yuma Valley probably in 1966. Senator Wash Dam is to be in operation about July 1966. The river is scheduled to be channelized from Imperial Dam to Morelos Dam beginning in 1966.
CONFIDENTIAL